[Elecraft] Thoughts about K2 freq shift & FINE RIT...

[Steve Kallal]

I've really loved the K2 since getting one second hand back in July. I've
added the KPA100, KSB2 and the K160RX options.

But there is one really sore point with me. That is the small frequency
shift when changing filters. It is not a big issue when using CW or SSB. I
can live with that. But it is a real sore point with the digital modes. To
be fair, I was aware of this before building the KSB2 option. I didn't
except to get back into the digital modes again, and have mostly been on CW
the past few months. I have other rigs for digital use, but the K2 receiver
is really fantastic.

I understand there is a FINE RIT feature that can correct this frequency
shift. I have the RTTY mode filters set up as:

FL1 OP1
FL2 1000 Hz
FL3 500 Hz
FL4 250 Hz

These cover most of my digital needs, depending on which mode.

The common fix for this problem is to use the tx frequency lock feature in
most of the digital comm software. Can I assume that the tx and rx
frequencies will match if I use the same filter for tx and rx? In my case,
this would be the OP1 filter. I could tune to the other station's frequency
in FL1 (OP1), before locking the tx frequency in the software. Once I lock
the tx frequency, I should be free to choose a narrower filter for rx.

Again, can I assume the tx and rx frequencies will be matched if I use the
tx filter?

Next I'd like to ask about FINE RIT. A reading of the manual and this
reflector tells me there are a number of variables affecting FINE RIT. It
has a finer frequency correction on the lower bands. And the shift amount
could change even within the same band. Also the FINE RIT correction needed
may change from filter to filter.

How can I determine the correct FINE RIT value needed for each band / filter
width combination?

It would help if I had a stable frequency source for each band and frequency
in question. The XG1 only works at 7.040 MHz, plus harmonics. 7.070 is a
popular digital frequency. I don't know if the frequency shift will vary
much on 40 meters when 30 kHz apart. The other bands are 80, 30, and 20
meters right now.

My goal is too make up a little chart telling me what FINE RIT value to use
with each band / filter width combination. It would still be a hassle, but I
could live with it, if it corrects my shift when using narrower filters.

The other digital gotcha with the K2/100 is the heat sink. I've been able to
get a large 4 inch muffin fan on top of the KPA100 heat sink and easily run
50 watts without excessive heating. It also helps some to keep in the
internal fan set to HI, but then I have to set it back to NOR when I am not
transmitting digital signals. It even gets warm when running CW at full
power, but not too bad.

Thanks in advance for any suggestions or comments!

73,

Steve N6VL
K2/100 #2289